The present invention relates to a digital wireless transmission and reception system, a transmission and reception device, and a method of transmission and reception, in which quality of communication is improved.
There are a number of methods for improving quality of communication in the digital wireless transmission such as an error-correction coding, a diversity transmission and reception, and a combination of them. A well-known method of error-correction coding among the above is a convolution coding having a superior -performance in the error correction. One example is a newly devised method which combines interleaving and puncturing with the convolution coding, as disclosed in Japanese Patent Laid-Open Publication No. H08-298466. A method of the prior art for improving quality of communication using a combination of the convolution coding, the puncturing and the time-diversity will be briefly described by referring to FIGS. 8A and 8B.
In a transmission device 800 of FIG. 8A, a series of information data 851 to be transmitted is punctured (thinning-out process) in a unit of a fixed amount of data block by a puncturing unit 802 in order to reduce an amount of communication traffic in a transmission pathway, after it is convolution-coded by a convolutional coding unit 801. A puncturing (thinning-out) location within the data block is stored as a puncturing pattern in a puncturing pattern generator 803, from where it is supplied to the puncturing unit 802.
An example shown in FIG. 8B will be described now in detail. A series of input information data {a0, b0, c0, d0 . . . } is converted into a series of convolution-coded data {a1, a2, b1, b2, c1, C2, d1, d2, . . . } by the convolutional coding unit 801 having a constraint length of 3 and a coding rate of 1/2. The puncturing unit 802 removes b2, d1, etc., and outputs a series of punctured data {a1, a2, b1, c1, C2, d2, . . . }, when a puncturing pattern 803b is supplied from the puncturing pattern generator 803. This series of punctured data is a combination of a series of data {a1, b1, c1, e1, . . . }, which is obtained by deleting data corresponding to a0 position in an upper row of the puncturing pattern 803b from a series of data {a1, b1, c1, d1, e1, . . . } corresponding to the upper row of the puncturing pattern 803b out of the foregoing series of convolution-coded data, and another series of data {a2, c2, d2, e2, . . . }, which is obtained by deleting data corresponding to a0 position in a lower row of the puncturing pattern 803b from a series of data {a2, b2, c2, d2, e2, . . . } corresponding to the lower row of the puncturing pattern 803b out of the series of convolution-coded data.
A time-diversity modulator/transmitter 804 repeats modulation and transmission of the series of punctured data for a predetermined number of times in response to a diversity transmission timing control signal supplied by a diversity transmission timing controller 805 at intervals of a predetermined time.
In a receiving device 810, the predetermined time for the transmission device 800 to repeat the time-diversity transmission is set in advance with a diversity reception timing controller 811, so that the diversity reception timing controller 811 outputs a timing control signal for starting a time-diversity reception according to the set time. A time-diversity receiver/demodulator 812 receives and demodulates a signal transmitted repeatedly in response to the control signal of a time-diversity reception timing, and outputs a series of demodulated data of every diversity branch (every repeat time). In this example, description is being made on an assumption that a result of demodulation for each symbol in the series of demodulated data is a quantized data in a resolution of four bits, and a mark and a space have their respective values equivalent to xe2x88x927 and +7 under the condition of no influence of noises.
A puncturing pattern generator 813 stores a puncturing pattern, which is identical to the puncturing pattern 803b used in the puncturing unit 802 of the transmission device. A depuncturing unit 814 uses this puncturing pattern to depuncture the series of demodulated data of every diversity branch, and outputs a series of depunctured data of every diversity branch. The depuncturing is a process in which the punctured position is filled with a dummy data such as a value of 0 corresponding to a middle value between the soft decision value of xe2x88x927 corresponding to a mark and the soft decision value of +7 corresponding to a space, for example. In the case of the foregoing series of punctured data {a1, a2, b1, c1, c2, d2, . . . }, the depuncturing unit 814 outputs a series of depunctured data {a1, a2, b1, 0, c1, c2, 0, d2, . . . }.
The series of depunctured data of every diversity branch obtained here is combineed symbol by symbol in a unit of block by a combining unit 815, and they are convolution-decoded with a method such as the Viterbi soft quantization by a convolutional decoding unit 816, which in turn outputs a series of decoded information data. There may be a case where the depuncturing and the combining are reversed in their order of transaction.
The devices can thus achieve an improvement in quality of communication for both of the error-correction coding and diversity with the structure as described above, by performing punctured-convolution-coding and time-diversity transmission on the information data to be transmitted, and also combining and depunctured-convolution-decoding after time-diversity reception of the data at the receiving side.
However, the structure of FIGS. 8A and 8B punctures certain identical locations in the series of convolution-coded data (error-correction code word) in each of the repeated transmissions by way of the time-diversity transmission. Therefore, these certain punctured locations and vicinity of them become susceptible to noises, as they become low in likelihood when convolution-decoding them, since they are treated as values having a large length between codes from both of the mark and the space at the receiving side.
A transmission and reception system of the present invention comprise a transmission device, a receiving device, and a communication pathway between them. The transmission device includes the following elements:
(1) a convolutional coding unit for convolution-coding a series of input data, and outputting a series of convolution-coded data;
(2) a puncturing unit for puncturing the series of convolution-coded data by using a plural form of puncturing patterns individually, and outputting a plurality of series of punctured data; and
(3) a modulator/transmitter for modulating and transmitting the plurality of series of punctured data via at least one communication pathway.
And the receiving device includes the following elements:
(1) a receiver/demodulator for receiving and demodulating a signal transmitted by the transmission device through the communication pathway, and outputting a plural variety of series of demodulated data;
(2) a depuncturing unit for depuncturing the plural variety of series of demodulated data by using each of the plural form of puncturing patterns that is identical to the one used by the puncturing unit, and outputting a plural variety of series of depunctured data;
(3) a combining unit for combining the plural variety of series of depunctured data, and outputting a result of combining; and
(4) a convolutional decoding unit for convolution-decoding the result of combining, and outputting a decoded data. The transmission and reception system transmits and receives via at least one communication pathway each of the plural variety of series of error-correction coded data obtained by puncturing and convolution-coding the identical series of information data with the plural form of puncturing patterns.
Also, A transmission and reception system of the present invention comprises a transmission device and a receiving device, and that the transmission device includes the following elements:
(1) a convolutional coding unit for outputting a series of input data by convolution-coding them;
(2) a first multiple puncturing pattern generator for generating a predetermined plural form of puncturing patterns having an identical puncturing rate, but different in block pattern of puncturing with one another;
(3) a puncturing unit for puncturing the series of convolution-coded data by using each of the predetermined plural form of puncturing patterns supplied by the first multiple puncturing pattern generator, and outputting a predetermined plurality of different series of punctured data;
(4) a diversity transmission timing controller for outputting a diversity transmission timing control signal for carrying out transmission for a plural number of times at intervals of a predetermined time;
(5) a time-diversity modulator/transmitter for modulating and transmitting the predetermined plurality of different series of punctured data one by one as diversity transmission data at intervals of the predetermined time in response to the diversity transmission timing control signal. The receiving device includes the following elements:
(1) a diversity reception timing controller for outputting a predetermined diversity reception timing control signal for carrying out a reception of the signal transmitted with time-diversity transmission at intervals of the predetermined time;
(2) a time-diversity receiver/demodulator for receiving and demodulating each of the signals transmitted for a plural number of times by the transmission device in response to the diversity reception timing control signal, and outputting individual series of demodulated data;
(3) a second multiple puncturing pattern generator for generating puncturing patterns, which are identical to those generated by the first multiple puncturing pattern generator;
(4) a depuncturing unit for depuncturing each of the series of demodulated data in quantity corresponding to the predetermined number of diversity receptions output from the time-diversity receiver/demodulator by using the predetermined different form of puncturing patterns supplied from by the second multiple puncturing pattern generator, and outputting a plural number of series of depunctured data;
(5) a combining unit for combining the predetermined plural number of series of depunctured data output by the depuncturing unit, symbol by symbol in a unit of block, and outputting a result of combining; and
(6) a convolutional decoding unit for convolution-decoding the result of combining, and outputting a decoded data.
The transmission and reception system, the transmission and/or reception device, and the method of transmission and/or reception executes the diversity transmission and reception of a plurality of different series of error-correction code word, as individual diversity branch data, by obtaining them through puncturing and convolution-coding the identical series of information data with different forms of puncturing patterns. Accordingly, the present invention is able to prevent a likelihood of certain information data from declining, and to further improve a quality of communication.